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Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence

Konca, A. Ozgun and Avouac, Jean-Philippe and Sladen, Anthony and Meltzner, Aron J. and Sieh, Kerry and Fang, Peng and Li, Zhenhong and Galetzka, John and Genrich, Jeff and Chlieh, Mohamed and Natawidjaja, Danny and Bock, Yehuda and Fielding, Eric J. and Ji, Chen and Helmberger, Don V. (2008) Partial rupture of a locked patch of the Sumatra megathrust during the 2007 earthquake sequence. Nature, 456 (7222). pp. 631-635. ISSN 0028-0836. doi:10.1038/nature07572.

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The great Sumatra–Andaman earthquake and tsunami of 2004 was a dramatic reminder of the importance of understanding the seismic and tsunami hazards of subduction zones [1,2,3,4]. In March 2005, the Sunda megathrust ruptured again, producing an event [5] of moment magnitude (Mw) 8.6 south of the 2004 rupture area, which was the site of a similar event in 1861 (ref. 6). Concern was then focused on the Mentawai area, where large earthquakes had occurred in 1797 (Mw = 8.8) and 1833 (Mw = 9.0) [6,7]. Two earthquakes, one of Mw = 8.4 and, twelve hours later, one of Mw = 7.9, indeed occurred there on 12 September 2007. Here we show that these earthquakes ruptured only a fraction of the area ruptured in 1833 and consist of distinct asperities within a patch of the megathrust that had remained locked in the interseismic period. This indicates that the same portion of a megathrust can rupture in different patterns depending on whether asperities break as isolated seismic events or cooperate to produce a larger rupture. This variability probably arises from the influence of non-permanent barriers, zones with locally lower pre-stress due to the past earthquakes. The stress state of the portion of the Sunda megathrust that had ruptured in 1833 and 1797 was probably not adequate for the development of a single large rupture in 2007. The moment released in 2007 amounts to only a fraction both of that released in 1833 and of the deficit of moment that had accumulated as a result of interseismic strain since 1833. The potential for a large megathrust event in the Mentawai area thus remains large.

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URLURL TypeDescription Information ReadCube access
Avouac, Jean-Philippe0000-0002-3060-8442
Sladen, Anthony0000-0003-4126-0020
Meltzner, Aron J.0000-0002-2955-0896
Sieh, Kerry0000-0002-7311-2447
Fielding, Eric J.0000-0002-6648-8067
Ji, Chen0000-0002-0350-5704
Additional Information:© 2008 Nature Publishing Group. Received 30 May; accepted 17 October 2008. This study was partly funded by the NSF (grant EAR-0538333) and the Gordon and Betty Moore Foundation. This is Caltech Tectonics Observatory contribution no. 93. We thank R. Burgmann for comments and suggestions. Supplementary Information is linked to the online version of the paper at
Group:Caltech Tectonics Observatory, Caltech Tectonics Observatory. Sumatran Plate Boundary, Seismological Laboratory
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Gordon and Betty Moore FoundationUNSPECIFIED
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Caltech Tectonics Observatory93
Issue or Number:7222
Record Number:CaltechAUTHORS:KONnat08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12535
Deposited By: Archive Administrator
Deposited On:16 Dec 2008 17:09
Last Modified:08 Nov 2021 22:29

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